The tubes and a fin-plate of a heat exchanger are united in one body by inserting the tubes through holes bored in the fin-plate and by expanding the tubes.
An example of a conventional tube expander for expanding the tubes is shown in FIG. 3. The tube expander in FIG. 3 has a reciprocating member 1, which is reciprocally moved up and down along guide shafts 5 and 5 by oil hydraulic cylinders 4 and 4, and multiple mandrels 41, each of which has a bullet having diameter which is larger than the inner diameter of the tube 50 which will be expanded and which is formed at the lower end thereof.
The lower end of each mandrel 41 is inserted into a corresponding tube 50, which is positioned below the lower end of each mandrel 41, to expand with the descending of the reciprocating member 1.
In the conventional tube expander, mandrels 41 are manually attached to or detached from the reciprocating member 1 according to the number or the arrangement of the tubes 50.
When mandrels 41 are attached or detached, the expanding work should be stopped. Thus, the efficiency of the work is reduced. Further, many types or many shapes of coolers presently exist, so that the number and the arrangement of the tubes 50 should be adapted to the coolers. Therefore, the efficiency of the expanding work is quite low because the attaching and the detaching are frequently requested during the expanding work.
To solve the above noted disadvantages, a tube expander, which is not required to attach and to detach mandrels when the number and the arrangement of tubes are changed, is disclosed in Japanese Patent Publication No. 1-16213. As illustrated in FIG. 4, a fixture 6 of mandrels 41 is provided on a reciprocating member 1 of the tube expander. There are bored through-holes through which the mandrels 41 are inserted in the fixture 6. The head sections of the mandrels 41 can project upward from the upper face of the fixture 6 but they are engaged so as not to move downward. Further, a plate 53 having multiple holes 52 is assembled on the upper face of the fixture 6. Further, a plate having multiple holes 52 shown in FIG. 6 is assembled on the upper face of the fixture 6.
In this expander, the head sections of the mandrels 41 corresponding to the holes 52 are not pressed by the plate 53, so that they project upward from the holes 52. More specifically the mandrels 41 corresponding to the holes 52 are not used for expanding tubes. If the pattern of holes, which is designed to press specific head sections of the mandrels 41 for expanding tubes, is defined beforehand, only the specific mandrels 41 which are needed will be moved downward. If plates 53, which individually have different patterns of holes 52, are prepared and set in a cartridge 26, the plate 53 having a desired pattern can be assembled on the upper face of the fixture 6 by an arm 33, which is moved in the right-left direction and is rotated by an oil hydraulic cylinder 30, etc. Note that, the up-down movement of the cartridge 26 is executed by a rod 28 of an oil hydraulic cylinder.
In the tube expander disclosed in Japanese Patent Publication No. 1-16213, once the maximum number of mandrels are attached to the fixture, it is not necessary to attach and detach the mandrels even if the number and the arrangement of the tubes of the heat exchanger are changed. Thus, the efficiency of the tube-expanding work can be increased.
However, in the above-described tube expander, it is necessary to prepare plates for the desired patterns. Therefore, if a plate having the desired pattern is not prepared, mandrels should be manually attached or detached, so that the efficiency will be quite low. Further, it is necessary to precisely make the plates because the locations of the mandrels, having head sections projecting upward from the fixture, must coincide with the locations of the holes.